1. Field
Example embodiments relate to semiconductor devices, and more particularly, to channel layers and semiconductor devices including the same.
2. Description of the Related Art
Transistors are commonly used as switching or driving elements in electronic devices. For example, a thin film transistor (TFT) is a type of transistor that can be formed on a glass or plastic substrate and is often used to switch and/or drive flat panel display apparatuses (e.g., liquid crystal displays and organic light emitting displays).
In order to improve the operational characteristics of transistors, attempts have been made to utilize oxide semiconductors as the transistor channel layer (e.g., a conventional oxide transistor). This conventional method is mainly employed for manufacturing TFTs for flat panel displays. However, in a conventional oxide transistor it is difficult to achieve a desired threshold voltage simultaneously with improved operational characteristics.
For example, a conventional oxide transistor generally uses an n-type oxide layer as the channel layer. To obtain improved operational characteristics including a high ON/OFF current ratio and a small subthreshold slope (SS), the carrier density and crystallinity of the n-type oxide layer may be increased and/or improved, resulting in increased and/or improved carrier mobility. Conversely, in order to obtain a desired threshold voltage, a reduced carrier density of the n-type oxide layer may be required and carrier mobility may be reduced. If the carrier density is reduced to obtain a desired threshold voltage, the ON/OFF current ratio may be reduced and the SS increased, thereby degrading the operational characteristics of the transistor. If the carrier density of the n-type oxide layer is increased to improve operational characteristics, the threshold voltage may become negative (−) and may prevent the manufacture of enhancement mode transistors.